Recently, a secondary battery, which can be charged and discharged, has been widely used as an energy source for wireless mobile devices. In addition, the secondary battery has attracted considerable attention as a power source for devices which require high output and large capacity, such as electric vehicles (EV), hybrid electric vehicles (HEV), and plug-in hybrid electric vehicles (Plug-in HEV), which have been developed to solve problems, such as air pollution, caused by existing gasoline and diesel vehicles using fossil fuels.
Small-sized mobile devices use one or several battery cells for each device. On the other hand, middle or large-sized devices, such as vehicles, use a battery module having a plurality of battery cells electrically connected to each other because high output and large capacity are necessary for the middle or large-sized devices.
Preferably, a battery module is manufactured so as to have as small a size and weight as possible. For this reason, a prismatic battery or a pouch-shaped battery, which can be stacked with high integration and has a small weight to capacity ratio, is usually used as a battery cell of a middle or large-sized battery module. In particular, much interest is currently focused on the pouch-shaped battery, which uses an aluminum laminate sheet as a sheathing member, because the pouch-shaped battery is lightweight and the manufacturing cost of the pouch-shaped battery is low.
In addition, the battery module is configured to have a structure in which a plurality of battery cells is combined. In a case in which overvoltage is applied to some of the battery cells, overcurrent flows in some of the battery cells, or some of the battery cells overheat, therefore, safety and operation efficiency of the battery module are seriously concerned. For this reason, it is necessary to provide means to detect and control such overvoltage, overcurrent, or the overheating.
Consequently, voltage sensors are connected to the respective battery cells to check and control operation states of the battery cells in real time or at predetermined time intervals. However, installation or connection of such detection means very complicates a process for assembling the battery module. In addition, there is a possibility that a short circuit may occur due to a plurality of wires for the detection means.
In addition, as a secondary battery is used as a power source for vehicles as the result of extension in an application range of the secondary battery, it is necessary to provide fastening members to retain stable contact states of the detection means even when string impact or vibration is applied to the secondary battery.
In case of lithium ion secondary batteries, on the other hand, it is necessary to measure voltages of the respective batteries using a voltage sensing unit in order to check states of the respective batteries. For this reason, safety of the batteries is seriously concerned in a case in which a short circuit occurs in the voltage sensing unit.
In addition, protection of the voltage sensing unit when the safety of the batteries is seriously concerned is very important for a battery system.
Consequently, there is a high necessity for a battery module that is compact and exhibits improved safety while fundamentally solving the above problems.